1. Field of the Invention
The present invention relates to a liquid delivery device, a liquid chromatograph, and a method for operation of said liquid delivery device.
2. Description of the Related Art
Any liquid chromatograph is provided with a liquid delivery device, among which is that of reciprocating plunger type. A conventional one of that type usually has two cylinders in each of which a plunger reciprocates, so that it delivers a liquid continuously, with two cylinders repeating sucking and discharging alternately.
Liquid delivery in this manner takes a certain length of time until the cylinder pressure reaches the discharge pressure because the liquid is compressed when the liquid, which has been suck up into the cylinder, is forced out by the plunger. As soon as the liquid is pressurized and the cylinder pressure reaches the discharge pressure, the valve at the discharge side is opened to deliver the liquid.
The drawback of such operation lies in the difficulties of detecting that the cylinder pressure is equal to the discharge pressure and the error of detection that prevents accurate control. This drawback leads to pulsation of liquid delivery that occurs in synchronism with the frequency of plunger movements. Such pulsation causes errors in liquid chromatography as described in Patent Documents 1 and 2.
Patent Document 1: Japanese Patent No. 3491948
Patent Document 2: Japanese Patent No. 3709409